Marking compositions

Abstract

A marking composition may include an aqueous carrier and thermochromic capsules. The thermochromic capsules may include a leuco dye, an activator, and a temperature regulator. The thermochromic capsules may have a volume average size effective to resist temperature-mediated discoloration at a temperature of at least up to 40° C. by dissipating heat. In some embodiments, the marking composition marks a substrate with a substantially erasable mark, for example, in response to frictional contact with an eraser.

What is claimed is: 
     
         1 . A marking composition comprising:
 an aqueous carrier; and   thermochromic capsules comprising a leuco dye, an activator, and a temperature regulator,   wherein the thermochromic capsules have a volume average size effective to resist temperature-mediated discoloration at a temperature of at least up to 40° C. by dissipating heat.   
     
     
         2 . The composition of  claim 1 , wherein the thermochromic capsules have a volume average size in a range from 1 micron to 10 microns. 
     
     
         3 . The composition of  claim 1 , wherein the composition is configured to mark a substrate with a mark that changes appearance in response to frictional contact with an eraser. 
     
     
         4 . The composition of  claim 3 , wherein the mark is substantially erasable in response to the frictional contact. 
     
     
         5 . The composition of  claim 3 , further comprising a non-thermochromic colorant, wherein the mark is configured to change color in response to the frictional contact, and wherein the non-thermochromic colorant is present in a range of from 0.1% to 40% by weight. 
     
     
         6 . The composition of  claim 1 , wherein the thermochromic capsules are configured to resist temperature-mediated discoloration at a temperature of up to 50° C. 
     
     
         7 . The composition of  claim 1 , wherein the thermochromic capsules have a volume average size in a range from 1 micron to 5 microns. 
     
     
         8 . The composition of  claim 1 , wherein the thermochromic capsules are present in a range of from 5 to 70% by weight. 
     
     
         9 . The composition  claim 1 , wherein the aqueous carrier is present in a range of from 10 to 80% by weight. 
     
     
         10 . The composition of  claim 1 , further comprising a co-solvent comprising a humectant. 
     
     
         11 . The composition of  claim 1 , further comprising a defoamer comprising one or more of silicones, insoluble oils, stearates, glycols, silicates, or talc. 
     
     
         12 . The composition of  claim 11 , wherein the defoamer comprises an emulsion of a polyether siloxane copolymer. 
     
     
         13 . The composition of  claim 1 , further comprising a biocide present in a range of from 0.01 to 5% by weight. 
     
     
         14 . The composition of  claim 13 , wherein the biocide comprises sodium omadine. 
     
     
         15 . The composition of  claim 1 , wherein the composition has an alkaline pH. 
     
     
         16 . The composition of  claims 15 , wherein the composition comprises a base, wherein the base comprises an amine, an amino acid, or tris(hydroxymethyl)aminomethane. 
     
     
         17 . A marking composition comprising:
 a thermochromic slurry, the thermochromic slurry comprising thermochromic capsules comprising a leuco dye, an activator, and a temperature regulator;   water;   glycerol;   a defoamer comprising an emulsion of a polyether siloxane copolymer; and   a biocide comprising sodium omadine,   wherein the thermochromic capsules have a volume average size from 1 micron to 10 microns so that the composition is configured to resist temperature-mediated discoloration at a temperature of at least up to 40° C., and   wherein the composition has a pH in a range of from 7.5 to 11.   
     
     
         18 . The composition of  claim 17 , further comprising a non-thermochromic colorant. 
     
     
         19 . The composition of  claim 17 , comprising:
 60.00% by weight of the thermochromic slurry, which is a green thermochromic slurry;   28.97% by weight of water;   10.00% by weight of glycerol;   1.00% by weight of the defoamer; and   0.03% by weight of sodium omadine.   
     
     
         20 . The composition of  claim 17 , comprising:
 50.00% by weight of the thermochromic slurry, which is a green thermochromic slurry;   28.97% by weight of water;   10.00% by weight of glycerol;   10.00% by weight of the non-thermochromic colorant;   1.00% by weight of the defoamer; and   0.03% by weight of sodium omadine.